Recently, there has been a remarkable advance in technology of a disk drive (hereinafter also called a disk recording and reproducing unit) for performing recording and reproducing operation on a disk-like recording medium (hereinafter also called a recording medium) such as a hard disk and optical disk, and use is expanding in various fields in addition to its conventional use for computers. Such a disk drive is further required to be capable of higher density recording, stable recording and reproducing without damage to recording medium or the head slider even in case of receiving disturbance such as shocks, and is also required to be reduced in size so that it can be mounted on portable equipment.
As an example of a head support device of a disk drive having a conventional floating type head, a conventional head support device in a magnetic recording and reproducing unit such as a hard disk drive will be described by using the drawings.
FIG. 17 is a plan view showing a configuration of a head support device of a conventional magnetic recording and reproducing unit, and also showing a relationship between the head support device and magnetic recording medium (hereinafter also called disk).
In FIG. 17, head support arm 108 of head support device 100 comprises support arm 102 which is relatively low in rigidity, plate spring 103, and support arm 104 which is relatively high in rigidity, and head slider 101 provided with a magnetic head (not shown) is disposed on an underside of one end portion of the support arm 102.
Also, magnetic recording medium 107 is arranged so as to be rotated by spindle motor 109, and when the magnetic recording and reproducing unit is operated, the magnetic head mounted on the head slider 101 obtains a given amount of floatation due to a relationship between buoyancy created by air flow produced by rotation of the magnetic recording medium 5107 and activation of the head support device 100 which activates the head slider 101 toward the magnetic recording medium 107.
The head support device 100, during recording and reproducing operations, is rotated about bearing portion 105 via action of voice coil 106 disposed on the support arm 104, and thereby, the magnetic head mounted on the head slider 101 is positioned against a desired track of the magnetic recording and reproducing medium 107 in order to execute the recording and reproducing operation.
Next, configuration and action of a conventional head support device will be described in detail with reference to FIG. 18.
FIG. 18 is a perspective view of an essential portion of head support arm 108 comprising support arm 102, and head slider 101, in a conventional head support device. The head slider 101 is fixed on tongue-like portion 113 disposed at an end of flexure 115. Also, another end of the flexure 115 is fixed on the support arm 102. For example, a ginbal spring is used as the flexure 115, which is configured so as to be able to pitch and roll against the head slider 101. The head slider 101 is fixed onto the flexure 115, for example, by using adhesive, while the flexure 115 is fixed onto the support arm 102, for example, by welding. An end portion of support arm 102 is provided with dimple 114 which serves to apply a load to the head slider 101, and a predetermined load is applied to the head slider 101 via the dimple 114. The configuration of the head support arm 108 includes the support arm 102 having the dimple 114, the flexure 115 having the tongue-like portion 113, and the head slider 101.
By using such head support arm 108, when a recording and reproducing operation is executed on a magnetic recording and reproducing medium 107 (not shown in FIG. 18) while being rotated, the head slider 101 is subjected to three forces such as a load applied via the dimple 114, a positive force that acts to cause the head slider to rise up from the magnetic recording medium due to air flow, and a negative force that acts to cause the head slider to approach the magnetic recording medium, and then, the head slider 101 is floated due to balance of these forces, and in a state of maintaining an amount of floatation, the head slider executes the recording and reproducing operation via an information conversion element (not shown) while driving a rocking device for positioning the head slider to a predetermined track position.
However, in the conventional disk drive, when external shocks are applied to the unit, the head slider bumps against or comes into contact with a recording medium, causing the head slider and the recording medium to be worn or damaged, which may sometimes result in breakdown of data or damage to the disk drive. Accordingly, a method for preventing external vibration from being transmitted to a main body of the disk drive is proposed (for example, refer to Japanese Laid-open Patent H9-153277) in that there is provided a fitting member for receiving external vibration, and a main body of the disk drive is bonded to the fitting member by using a flexible heat insulating member. Thus, a disk drive which is strong against external vibration can be realized, but the disk drive in its entirety is relatively large in size, and it is difficult to mount such a disk drive in portable equipment required to be small-sized and light-weight.
Accordingly, it is necessary to improve shock resistance of a head slider and support arm, or head support arm itself, and at the same time to achieve objectives such as miniaturization of a disk drive and improvement of its shock resistance. Particularly, since the head slider is opposed to a recording medium while maintaining a delicate amount of floatation against the recording medium, it is required to prevent the head slider and the recording medium from being seriously damaged when shocks are applied thereto. However, a shape of a surface of the head slider opposing the recording medium is not usually devised for a purpose of improving shock resistance, but in many cases, improvements are made in various ways in order to stabilize an amount of floatation at an air outflow side of the head slider where an information conversion element is disposed, as against variations of skew angle and atmospheric pressure.
For example, there is a proposal of a head slider configuration such that a positive pressure generating section for generating great positive pressures, and a negative pressure generating section for generating negative pressures, are concentrated at an air outflow side of the head slider in order to increase rigidity of an air layer at the air outflow side (for example, refer to Japanese Laid-open Patent H-10-283622). In such a configuration, when the head slider pitches and changes in its floating posture, there exists a point as a focal point at which an amount of floatation does not vary, and a position of this focal point can be near an air outflow end of the head slider where an information conversion element is disposed. In this way, it is possible to execute stable recording or reproducing of information almost without change in an amount of floatation of the head slider near the information conversion element due to action of positive and negative pressures even in case of variations of skew angle, atmospheric pressure, external forces due to rocking, or load.
Also, as a head slider structure for reliably realizing a low-level amount of floatation, there is a proposal of a head slider configured in that there exists a position as an immovable point at which an amount of floatation does not vary, and the immovable point is positioned at an air outflow end side of the head slider (for example, refer to Japanese Laid-open Patent H8-227514). That is, in a head slider wherein, when a push load is applied in a direction of a recording medium, a positive pressure is generated that acts to float the head slider with viscous flow of air generated by rotation of the recording medium, and a negative pressure is generated by air flowing into a groove formed in a head slider surface, the head slider is constructed such that a center of negative pressure generation is positioned a little closer to an air inflow side of the head slider than to an action point of the push load.
Due to this structure, when an external force (moment) acts on the head slider to move it upwardly, a negative force acts to cope with the external force so that the head slider can be maintained in a stable state. That is, it is disclosed that even when an external force acts to move the head slider upwardly, a negative force will act against the external force, and since the air outflow end side of the head slider fitted with an information conversion element is substantially a rotational center of balance or an immovable point, a distance from the information conversion element to a recording medium surface remains almost unchanged.
As described above, in a head support device of a magnetic recording and reproducing unit, it has been necessary to apply a predetermined load to the head slider in a direction of a magnetic recording medium in order to prevent off-tracking of a magnetic head, mounted on the head slider, by maintaining the head slider in a stable state of floating even in case of external shock or vertical movement of the magnetic recording medium during a recording and reproducing operation. Also, during a recording and reproducing operation of a magnetic recording medium, it has been necessary for a head support device to have appropriate flexibility so that a head slider may follow vertical movement or the like of the magnetic recording medium. Further, in order to reduce size of a magnetic recording and reproducing unit, to reduce thickness in particular, it has been necessary to thin a head support device in a direction vertical to a magnetic recording medium surface.
However, in a conventional head support device, as described above, since it is configured in that a support arm is connected by a plate spring to a coupling portion, it is required to satisfy incompatible requirements in order to satisfy various requirements of the head support device. That is, specifically, firstly to obtain a stable floating status of a head slider with a magnetic head mounted thereon, it has been necessary for the plate spring to have a reaction force that is sufficient to apply a necessary load to the head slider.
Also, it has been necessary for the head support device to have appropriate flexibility in order to prevent a load applied by the head slider to a magnetic recording medium from being varied due to a vertical movement of the magnetic recording medium, or manufacturing variations or the like of a distance between the head slider and the magnetic recording medium of every magnetic recording and reproducing unit in mass-production. In the conventional head support device, it has been designed that there is provided a notch in plate spring 103 as shown in FIG. 17, which serves to lower rigidity of the plate spring 103 and to lessen a spring constant for a purpose of providing the date spring with flexibility.
Also, in case the support arm is structurally thinned in order to lower rigidity of the plate spring, frequency at a main resonance point, that is so-called resonant frequency, is low and causes a vibration mode such as twisting when the head support device is moved for positioning, and consequently, it takes much time for settling a vibration mode generated, resulting in a shortening of access time.
Further, in the conventional head support device, since a center of gravity is positioned a little closer to the magnetic head than to the plate spring, when strong shock or the like is exteriorly applied to the magnetic recording and reproducing unit, buoyancy due to air flow generated due to rotation of a magnetic recording medium is unbalanced against an activating force of the head support device which activates the head slider toward the magnetic recording medium, and then a phenomenon takes place such that the head slider jumps from the magnetic recording medium. As a result, the head slider bumps against the magnetic recording medium and may cause magnetic damage or mechanical damage to the magnetic recording medium.
Also, in the above example of a head slider, to prevent variation of an amount of floatation at an air outflow end of the head slider where an information conversion element is disposed, a surface of the head slider opposing a magnetic recording medium is provided and a load action point is arranged so that an immovable point or focal point is positioned at the air outflow end of the head slider. Accordingly, even when a floating posture is changed due to variation of a skew angle, atmospheric pressure, or load, an amount of floatation can be stabilized at an air outflow end side where the information conversion element is disposed. However, comparing such variation with an exteriorly applied shock, the shock is far greater than the variation, and therefore, it cannot be said that the proposal described above is effective to cope with shocks.
That is, when a great shock is applied to the head slider of which the immovable point or the focal point is positioned at the air outflow end, there may arise a situation such that the head slider is of negative pitch angle; that is, an amount of floatation at the air inflow end side of the head slider is less than an amount of floatation at the air outflow end side of the head slider. In this case, it is unable to form an air layer between the surface of the head slider opposing a magnetic recording medium and a surface of the magnetic recording medium, and thus the head slider does not float at all and is damaged due to bumping against the recording medium.
Also, in the proposal, the point at which an amount of floatation remains unchanged even in case of variation in skew angle or the like is defined as the focal point, and the surface of the head slider opposing the magnetic recording medium is shaped so that the position corresponds to the air outflow end of the head slider. Thus, nothing is mentioned about whether or not the immovable point corresponds to the focal point when external shocks are applied to the head slider.
Further, regarding a proposal of a configuration such that a position at which an amount of floatation remains unchanged is an immovable point, and the immovable point is positioned at an air outflow end side of the head slider, an amount of floatation at the air outflow end side of the head slider can be controlled in a case of such a rotational moment as to move the head slider upwardly, but in a direction perpendicular to a recording medium surface, especially in a case of a downward shock applied to the recording medium surface, where the head slider may bump against the recording medium surface even due to a slight shock.
Moreover, in a disk drive mounted in portable equipment, it is necessary to reduce a diametric size of a recording medium and also to lower a recording medium rotating speed, and speed of air flow on a surface of a head slider opposing the recording medium becomes lower as compared with the prior art. In case the recording medium rotating speed is at a low level, when a negative pitch angle is generated at the head slider due to shock, an air layer cannot be formed, and a possibility of bumping against the recording medium is very much increased, but nothing is disclosed about this matter in the above examples.
The above problems are not peculiar to a magnetic recording and reproducing unit, and there have arisen similar problems in a disk drive having a floating type head such as an optical disk drive and optical magnetic disk drive.